The problem of aircraft flight safety is of current importance and includes a number of scientific, technical and organizational problems. One of the problems is to provide flight safety under conditions where the decisive factor is subjection of aircraft to high turbulence aerodynamic jets caused by generators moving near the aircraft, as well as by other objects, which undergo the airflows of high level of turbulence and vorticity.
It is well known that aircraft moving in the airspace generate the so called ‘wake vortices’.
The aircraft encounter with wake vortices of a generator, e.g. of another aircraft results in the substantial change of the attack and sideslip angles. The encountering aircraft is exposed to aerodynamic forces and moments that may throw it aside from the wake. This may cause accidents when flying at low altitudes, for example, during take-off and landing, as such disturbances cannot be counterbalanced by the aircraft controls in all cases.
Aircraft with low aspect wings and high wing load generate wake vortices of higher strength increasing the vortex danger.
A large body of research on wake transport and attenuation shows that the atmospheric factors such as wind, wind shift, stratification and turbulence play an important role in these processes.
There exists a potential to optimize the safe separations during landing, take-off and cruising flight by means of accurate prediction of wake vortex dynamics with due regard to current weather conditions, short-range weather forecast, and in-ground effects.
One of the main ways for solution of the safe flight problem, when the main factor is the aerodynamic wake, is the selection of flight modes ensuring the required safety level.
The development of airborne computer systems working in real time, estimating the danger level of aerodynamic disturbances that influence the aircraft and permitting the selection of methods for correction of the aircraft flight control for the purpose of best compensating the disturbances is beneficial for the problem decision.
Another problem, which may be called an informational one, is the problem of informing the pilot on the wake vortex location and the relative position of the aircraft in the prediction period of time.
The method and device for visualization of wake vortices by means of mathematical simulation on the basis of the known parameters of aircraft generating wake vortices with due account of atmospheric conditions are well known. According to the technical decision, the device uses a fast-response display where the simulated wake vortices generated by each aircraft located in the vicinity of the given aircraft are visualized (U.S. Pat. No. 5,845,874, A). However, if the given aircraft is surrounded by a great number of other aircraft, for example, in the vicinity of an airport, the display will show a great number of simulated wake vortices and it will be difficult to identify which wake vortices are of real danger for the aircraft and which ones could be ignored.
One of the most perspective ways of increasing flight safety is informing the pilot in real time on the forecasted location of dangerous wake vortices.
The airborne wake vortex alert system informing the aircraft crew on the risk of encounter with wake vortex area of another aircraft only when the system has determined that the encounter will occur after the predetermined time is well known (U.S. Pat. No. 6,177,888, A). The system provides the interaction between the both aircraft, the exchange of warning signals and of information on the current altitude, distance and bearing, wake path tracking with account of the local wind speed, and determines the distance or time needed for the aircraft to encounter the wake vortex area of another aircraft. The system displays the warning of the wake vortex area proximity when the needed distance or time is less than the given threshold. The wake vortex area size is calculated in each of the points distributed along the wake vortex path as a function of the distance between the point and the aircraft generating the wake.
However this system does not solve the problem of informing the pilot on the hazard level if the aircraft encounters wake vortices and does not suggest any correct maneuver to avoid the encounter.
In addition, the variety of aircraft operation conditions requires reduction of distances between the aircrafts, for example such the reduction during the consecutive take-offs or landings could increase the airport capacity.
The reliable knowledge of location and structure of wake vortices and their effect on aircraft flight would help to meet the conflicting requirements on the increase of flight efficiency and safety.
The airborne wake vortex alert system warning the pilot against the predicted hazard due to the presence of other aircraft in the aircraft vicinity (U.S. Pat. No. 6,211,808, B1) is well known. The system comprises a spherical antenna made of dielectric material that has eight sectors with a receiver in each to receive microwave signals reflecting from other aircraft located in the vicinity. However, the system is rather expensive and does not inform the pilot on the presence of hazardous air disturbances.
The technical decision related to the scheme and method to prevent collision of the aircraft path and wake vortices of another aircraft is well known (WO 00/71985). This method consists in determining the position, geometry and type of another aircraft wake vortices, which presence has been revealed by means of information received from the first aircraft airborne systems, from the second aircraft or from the aerodrome, determining the altitude of the second aircraft, the forecasted position of its wake vortices with due regard for the weather conditions, in particular, the wind velocity and direction, and ambient temperature, adjusting the received data with the reference table, or modeling the wake vortices with visualization of its location and path with respect to the first aircraft, and, finally, forecasting the intersection point of the wake and first aircraft paths with generation of the alarm signal if the intersection may occur. Basically, the method is used to provide safety of two aircraft flying in the airport terminal area and its implementation could result in increase of the first aircraft altitude over the second aircraft using the Traffic Alert and Collision Avoidance Systems. However, the first aircraft pilot receives visual information on all the vorticity areas that are suspected to be in the flight area of the first aircraft due to the presence of the second aircraft. Hence the first pilot could not have the real picture of dangerous vortices.
It is well known that the National Aeronautics and Space Administration (NASA), USA, gives much attention to the airport terminal area efficiency, in particular during take-off and landing. One of the directions for R & D works is development of the Aircraft Vortex Spacing System (AVOSS), which will combine the outputs of different systems and produce weather dependent dynamic criteria for wake vortex spacing (37th Aerospace Sciences Meeting & Exhibit, Jan. 11-14, 1999, Reno, Nev., NASA Langley Research Center, Hampton, Va.). The system represents the current and forecasting weather conditions, the models of wake vortex transport and decay under these weather conditions from the ground surface up to the altitude of the take-off and landing glideslopes, as well as performs the feedback for wake vortex behavior in real time.
The correlation of the wake vortex behavior with the predetermined sizes of the safety corridor and with the data on wake decay results in the required aircraft spacing. If the wakes exist longer than it was expected, the reduction of intervals between aircraft take-offs or landings is prohibited. The wake behavior is calculated for a number of landing ‘windows’ from the glideslope altitude to the runway threshold. However, this system has a number of restrictions such as the lack of due regard for the vertical wind, which may prevent the wake descent or produce its ascent; the lack of due regard for the ambient turbulence scale necessary for correct simulation of the wake decay; and some others. These restrictions may lead to contingency due to the discrepancy between predetermined wake vortex parameters at the dispatcher's disposal and the actual wake parameters. Besides, the use of the AVOSS will increase dispatcher workload raising the probability of wrong decisions.
It is well to bear in mind that the foreign safety systems are mainly designed for the use under the so called ‘Instrument Flight Rules’ (IFR) when the control of aircraft is carried out on the basis of the commands made by a flight controller, which are implemented either in directory or automatic mode on the aircraft board.
However, it is well known that the most critical juncture of things in operator activities is the correct decision in an emergency situation. It consists of two stages: identification of the situation and determination of the operating procedure to eliminate the emergency situation. Prior to performing each of the further actions the control officer should envisage his further steps. The perception of visual and voice signals in verbal form from long-term memory or from a display, or orally, needs a certain time under conditions of time deficiency. The time needed for perception of graphic symbols is far less. Identification of the situation with object indication permits improving the decision adequacy.
Moreover, the effect of such a physical factor as acceleration causes detraction of the pilot brain circulation, which may force even loss of the pilot consciousness under emotional and nervous tension. Therefore the information necessary for decision-making is preferable to place at the pilot or flight controller disposal before the occurrence of actual time for decision and in graphical symbols.